Non-fatal, self-inflicted injuries by adolescent and young adult females are major public health problems and researchers have found physiological evidence that this behavior may lead to a more serious psychological condition called borderline personality disorder.

University of Washington psychologists have discovered that adolescent girls who engage in behaviors such as cutting themselves have lower levels of serotonin, a hormone and brain chemical, in their blood. They also have reduced levels in the parasympathetic nervous system of what is called respiratory sinus arrhythmia, a measure of the ebb and flow of heart rate along with breathing.

“A low level of this measure of the parasympathetic nervous system is characteristic of people who are anxious and depressed and among boys who are delinquent. But this is the first study to show it among adolescent girls who engage in self-harming behavior,” said Theodore Beauchaine, UW associate professor of psychology.

The findings come from a study that also uncovered sharp disparities in the number of self-harming events and suicide attempts reported by the girls and their parents.

The research, headed by Sheila Crowell, a UW psychology doctoral student, focused on girls because self-harming behavior affects females far more often than it does males. The study included 23 girls, ages 14 to 18, who engaged in what psychologists call parasuicidal behavior. Participants were included if they had engaged in three or more self-harming behaviors in the previous six months or five or more such behaviors in their lifetime. An equal number of girls of the same ages who did not engage this behavior were enrolled as a comparison group.

The adolescents in the parasuicide group reported far more incidents of self-harming behavior than did their parents. Individuals engaged in this kind of behavior between 11 and 839 times. Their parents, however, reported a range of 0 to 205 incidents. Similarly, the girls reported more than three times the number self-harming behaviors with intent to die, 310 events versus 90, than their parents did. However, the girls and their parents were very close on the number of times an adolescent required medical attention.

Twenty of the girls, or 87 percent, reported at least one attempted suicide, but Crowell said this number is not that surprising in this population.

“You need to understand a person’s intent and the lethality of their attempts,” she said. “Did they take a small number of Tylenol or were they holding a loaded gun to their head?”

She noted cutting was the most common self-harming behavior in which the girls engaged. Eight-two percent of girls used instruments ranging from paper clips to kitchen knives and razors with the intent of hurting themselves.

“These attempts have to be taken seriously,” said Beauchaine. “These girls may be really at risk for later suicide, and in the long term there needs to be studies of the progression of self-harm attempts.”

To find physiological markers of self-harming behavior, the UW researchers showed both groups of adolescents a three-minute film clip from the movie “The Champ” depicting a boy with his dying father. Previous studies have shown the film can induce sadness. A number of different psychophysiological measures were collected from each of the girls before, while and after viewing the film clip. Following the viewing a small blood sample was taken to measure whole-blood serotonin.

The girls who engaged in self-harming behavior had lower levels of respiratory sinus arrhythmia in their parasympathetic nervous system while watching the film clip. These measures, the researchers argue, support the idea that the inability to regulate emotions and impulsivity can trigger self-harming behavior.

“This research supports the primary theory that borderline personality disorder is caused by an inability to manage emotions. These girls have an excessively strong emotional reactions and they have extreme difficulty in controlling those emotions,” said Beauchaine. “Their self-harming behavior serves to distract them from these emotions.”

Borderline Personality Disorder is far more serious than self-harming behavior and people with the condition have a very high suicide rate. An estimated 5.8 million to 8.7 million Americans, mostly women, suffer from borderline personality disorder. People with the condition have a multiple spectrum of disorders that are marked by emotional instability, difficulty in maintaining close relationships, eating disorders, impulsivity, chronic uncertainty about life goals and addictive behaviors such as using drugs and alcohol. They also have major impact on the medical system by being among the highest users of emergency and in-patient medical services.

Co-authors of the study are Elizabeth McCauley, UW professor of psychiatry and behavioral science; Cindy Smith a former psychiatrist at Children’s Hospital who is now in private practice; Adrianne Stevens, an incoming UW psychology graduate student, and Patrick Sylvers, a former UW student who is now a graduate student at Emory University. The study, published in the journal Development and Psychopathology, was funded by Seattle Children’s Hospital, the National Foundation for Suicide Prevention and the National Institute of Mental Health.